CN101081699B - A kind of ordered mesoporous silicon oxide and its rapid preparation method - Google Patents

Abstract

The invention discloses an ordered mesoporous silicon oxide and a rapid preparation method thereof. It uses a high-concentration solution of a triblock copolymer P123 as a template, and tetraethyl orthosilicate (TEOS) as a silicon source. Prepared quickly. The mesoporous silicon oxide material has high order degree, complete space group structure, large pore diameter, thick pore wall, good hydrothermal stability, simple process, quick and easy operation, and convenient operation. There is no aging process in the preparation, no need for high temperature and high pressure, no need to add pore-enlarging aids, and the template agent used is environmentally friendly and low in price, reducing the cost. After proper follow-up functionalization, the mesoporous material can prepare an adsorbent with good removal ability for target ions. It is an environmentally friendly material and can also be used to prepare high-flux and high-selectivity inorganic separation membranes. This material has broad scope of application and prospects.

Description

A kind of ordered mesoporous silicon oxide and its rapid preparation method

a technical field

The invention belongs to the field of ordered mesoporous materials, and in particular relates to an ordered mesoporous silicon oxide with a large-aperture three-dimensional bicontinuous pore structure and a rapid preparation method thereof.

Two background technology

Ordered mesoporous materials have the advantages of high specific surface area, narrow pore size distribution, continuously adjustable pore size within a certain range, and easy surface modification. It has great application potential in the fields of separation and catalysis. With the continuous deepening of the research on mesoporous materials, different types of series of mesoporous materials have been reported one after another. Among them, the ordered mesoporous silica with space group Ia3d has a helical bicontinuous cubic structure, which is characterized by The two sets of three-dimensional channels that are identical but not connected to each other have high symmetry and good connectivity, and are superior to two-dimensional and one-dimensional channel structures in terms of material diffusion and transmission. It can be used as microreactors for macromolecular reactions, catalyst supports, adsorbents, optical devices and sensor devices, etc., which undoubtedly shows broad application prospects. However, corresponding to this structure is the V1 region of the lyotropic liquid crystal phase diagram. For most surfactants, this phase region is relatively small, so this structure is difficult to synthesize.

Domestic scholars in the field of synthesis of mesoporous silica with space group Ia3d mainly focus on synthesizing mesoporous silica powder in water system under alkaline conditions. Acta Chemica Sinica, 2005, 63 (13): 1241-1244 published an article entitled "Synthesis of MCM-48 Mesoporous Molecular Sieves with High Heat and Hydrothermal Stability in Buffer System" published by Kong Lingdong et al. The mesoporous silica powder with pore diameter of 2.67nm and space group Ia3d was prepared by 2d crystallization with mixed cationic-nonionic surfactant as template in alkaline buffer system. The traditional method of synthesizing mesoporous silica with space group Ia3d is mostly hydrothermal synthesis or high-pressure synthesis, with harsh reaction conditions and long reaction time. Most of the products are powder, and the pore size is small and the pore wall is thin, which greatly limits its practical application. AdvancedMaterials, 2003, 15(22): 1893～1899, El-Safty and others published an article titled Fabrication ofcrystalline, highly ordered three-dimentional silica monoliths(HOM-n) with large, morphological mesopore structures, and they used the direct template method , using the non-ionic surfactant Brij56 (C ₁₆ EO ₁₀ ) as the template, methyl orthosilicate (TMOS) as the silicon source, and adding heptane and octane as auxiliary agents, a medium with space group Ia3d was prepared. Porous silicon oxide with pore diameters of 3.7nm and 3.9nm, respectively. However, the problem of this method is that the drying process needs to use a vacuum environment to remove the methanol hydrolyzed product of TMOS, and needs to add a pore-enlarging agent, which complicates the preparation of the material and increases the preparation cost.

Three invention content

The purpose of the present invention is to provide a method for rapidly preparing ordered mesoporous silicon oxide. It has simple process, mild reaction conditions, short time and easy operation. The prepared material has the characteristics of large pore diameter, thick pore wall, good hydrothermal stability and low cost.

An ordered mesoporous silica, characterized in that the reactants consist of the following components: tri-block copolymer P123 (PEO ₂₀ PPO ₇₀ PEO ₂₀ ), tetraethyl orthosilicate (TEOS), hydrochloric acid solution, and the final press The molar ratio of the materials is TEOS:P123:HCl=1:0.0367:0.0038.

The object of the present invention is achieved by the following technical scheme: the method for fast preparation of ordered mesoporous silicon oxide, it is with the high concentration solution of triblock copolymer P123 as template agent, orthoethyl silicate (TEOS) is Silicon source, hydrochloric acid solution reacts as catalyzer, it is characterized in that finish according to the following steps:

(1) According to the molar ratio of materials TEOS:P123:HCl=1:0.0367:0.0038, first take P123 in the reactor, add TEOS, stir in a water bath at 60°C until it is completely dissolved, and the dissolution process takes 1min to 2min;

(2) quickly add the hydrochloric acid solution of 0.05mol/L in the reaction solution, stir rapidly, form the sticky paste,

(3) Stand at room temperature for about 10 minutes to form a clear and transparent silica sol;

(4) Dry the above-mentioned sol at room temperature first, and then place it at 50°C for 8h-10h to form a xerogel;

(5) Heat treatment at 450° C. for 4 hours, and the heating and cooling rate is controlled at 1° C./min. After the sample temperature is cooled to room temperature, highly ordered mesoporous silica is obtained.

Among the above reactants, the high-concentration solution of triblock copolymer P123 is used as template agent, orthoethyl silicate (TEOS) is used as silicon source, and hydrochloric acid solution is used as catalyst for the reaction. The PPO block in the middle of the template molecule exhibits hydrophobic properties in aqueous solution, while the PEO blocks at both ends have affinity with water, so that the entire molecule exhibits amphiphilic properties, and can spontaneously form a large inner core under suitable conditions. Micelles, providing structure guidance for the synthesis of mesoporous silica. After the addition of hydrochloric acid solution, ethyl orthosilicate rapidly hydrolyzes, cross-links and reacts with high-concentration template agent micelles to form mesoporous silica sol.

In the above preparation method, the proportion of materials can be fixed, the amount of reagents can be enlarged or reduced, and the actual required sample amount can be prepared, while the structure of the prepared ordered mesoporous silica remains unchanged. The drying process of the solvent can be in the required container, such as watch glass, beaker, crucible, and can also be uniformly cast on the glass or plastic substrate to prepare a thin film.

Compared with the prior art, the present invention has the following advantages: (1) No need to use water or ethanol as a dispersing agent in the sol preparation process, but to directly form a uniform high-concentration mixing system between the silicon source and the template agent. After hydrochloric acid is added, the hydrolysis, cross-linking and interaction with the template micelles of the silicon source can be completed in a very short time, and the entire sol preparation process is completed within 15 minutes, and the preparation method is fast and simple; (2) The reaction conditions are mild , without high temperature and high pressure, without crystallization or aging process, without vacuum treatment, so it is simpler, time-saving and easy to operate. In addition, the templating agent used is cheap and environmentally friendly, and the preparation process does not need to add pore-enlarging aids, which reduces the cost, which makes this method have the characteristics of large-scale industrial production; (3) the mesoporous composite synthesized by this method The silicon oxide material has a high degree of order, a complete space group structure, a large pore size (5.69nm), a thick pore wall (15.02nm), and good hydrothermal stability. After appropriate follow-up functionalization, the mesoporous material can prepare an adsorbent with good removal ability for target ions, which is an environmentally friendly material; (4) The shape of the product can be adjusted according to actual application needs, such as: can be prepared into Membranes used in the field of separation and optics, or prepared as powder or block for the field of adsorption and catalysis, etc. The material can be directly used in the fields of adsorption, separation, electricity and optics, and can also be used as a catalyst carrier for catalytic reactions.

4. Description of drawings

The accompanying drawing is a schematic process flow diagram of the rapid preparation method of ordered mesoporous silicon oxide according to the present invention.

5. Specific implementation

The rapid preparation method of ordered mesoporous silicon oxide of the present invention adopts direct template method, with the high-concentration solution of triblock copolymer P123 as template agent, orthoethyl silicate (TEOS) as silicon source, in acidic quickly in the system. The final material molar ratio is TEOS:P123:HCl=1:0.0367:0.0038. The present invention will be described in further detail below in conjunction with the accompanying drawings.

In actual operation, the required amount of mesoporous silica can be prepared by fixing the ratio of materials and changing the amount of reactants. Taking the preparation of a 7.9g sample as an example, the specific operation steps are:

(1) Accurately weigh 14g of P123 into a three-necked flask, add 30mLTEOS, and stir in a 60°C water bath until completely dissolved;

(2) Add 10mL of 0.05mol/L hydrochloric acid solution rapidly to the reaction solution, stir rapidly to form a thick paste;

(3) Stand at room temperature for about 10 minutes to form a clear and transparent silica sol;

(4) Evenly cast the above sol on the glass substrate, first dry at room temperature for 24 hours, and then continue to dry at 50°C for 8 hours to form a xerogel;

(5) Heat treatment at 50°C for 4h, the heating and cooling rate is controlled at 1°C/min, and when the sample temperature drops to room temperature, highly ordered mesoporous silica can be obtained

The mesoporous silica material synthesized by this method has a high degree of order, complete space group structure, large pore diameter, thick pore wall, average pore diameter of 5.69nm, wall thickness of 15.02nm, specific surface area of 499.75m ² /g, and pore volume of 0.711 mL/g.

Subsequent functionalization treatment is carried out on the above-mentioned mesoporous silica with three-dimensional double continuous large pore size, and functional groups with adsorption activity are grafted in its pores, and an adsorbent with significant removal ability for harmful ions in water can be obtained, and the adsorption capacity is obvious Higher than that of two-dimensional functionalized materials prepared by the same method.

The mesoporous silica sol prepared by the above method is coated with a complete top layer membrane on the porous carrier, and the prepared inorganic separation membrane has the characteristics of high flux and high selectivity at the same time. The mesoporous silicon oxide prepared by the invention can also be used as a catalyst carrier to prepare microreactors for macromolecular catalytic reactions.

Claims (1)

1. method for preparing fast ordered meso-porous silicon oxide, it be highly concentrated solution with triblock copolymer P123 as template, tetraethoxy (TEOS) is the silicon source, hydrochloric acid soln reacts as catalyzer, it is characterized in that finishing according to the following steps:

(1) press the mol ratio TEOS of material: P123: HCl=1: 0.0367: 0.0038, get P123 earlier in reactor, add TEOS, 60 ℃ stirred in water bath to molten entirely;

(2) the rapid hydrochloric acid soln that adds 0.05mol/L in reaction solution stirs fast, forms the heavy-gravity mashed prod;

(3) leave standstill under the room temperature about 10min, form the silica sol of clear;

(4) above-mentioned colloidal sol is at room temperature dry earlier, place 50 ℃ to continue dry 8h～10h down again, form xerogel;

(5) 450 ℃ of following thermal treatment 4h, temperature rate is controlled at 1 ℃/min, treat that sample temperature is cooled to room temperature after, promptly obtain the mesopore silicon oxide of high-sequential.

Images